What is IAM?
Identity Access Management (IAM) is a way of how a user uses AWS resources. It empowers users to manage access to various AWS resources /services in a secure way.
AWS uses users/groups, policies via IAM to allow/disallow permission for specific or set of AWS resources.
via IAM it is not always required to use “root” credentials or root account to use any AWS service instead an AWS user can be assigned an IAM role related to specific service via which the respective AWS service can be accessed by user.